used Alphatiac resin hardwood and plywood

[paulwells66]

On my super combat streak I used alphatiac resin to glue the engine beams (hardwood) to the fuselage doublers. Trying to keep it light.
I've read posts where people say to use epoxy instead but when I look at woodworking sites they claim it's stronger than the wood itself.
I also used it to secure the plywood bellcrank platform.

has anyone done this and did it fail or was it ok?

thanks...kind of too late now for the combat streak...did go ahead and use mid cure epoxy for the engine mount on my voodoo.

[paulwells66]

yikes...scared...maybe go back and do epoxy fillets.  I also build an old VK Cherokee RC kit and did the same thing.
Oh well I guess I might be in for some unexpected excitement.

[paulwells66]

what did people use in the 50's? assuming there was no epoxy back then

[paulwells66]

I also don't understand the oxygen getting to it part...aren't all tight glue joints by nature not exposed to oxygen? be it a dovetail in a chair or a balsa nose block?

[paulwells66]

well you got me running scared now.  so what I will do is drill holes down the side and epoxy hardwood dowels to pin it in place.

[Tom Vieira]

i've had no issues doing exactly as you have done.  but i also slather things in finishing resin for fuel proofing.

glue a couple scrap pieces together and try to break em apart the next morning.....  Like any good adhesive, the substrate will break before the joint.

[Dan McEntee]

  Yes, as TJ suggested, do a test section. The thing you want to avoid is using it on large surfaces like plywood doublers. It may dry at the edges but farther in is where what Ty explains would come in. For motor mounts, apply clamps for pressure squeezes out excess glue and less air is needed and the joint is stronger for it. You could poke a bunch of pinholes through the balsa to let some air get through before you finish the wood. Even with using epoxy, you want to use a minimum and apply pressure where ever possible. Doing that test section and letting it sit for a few days, then testing to destruction may give you some peace of mind.  All glue joints should be as tight and gap free as possible for best strength. When "gap filling" CA glue came on the market it tended to make us a bit lazy in that respect. Tom Morris uses plain old Elmers glue for all of his construction, and once had a section of motor mount stock get glued to the glass surface he was building on. He gave it a whack with a hammer and a hard wood drift to break it loose and it popped a section of glass up! That ought to tell you something. When all is completed, then a coat of thinned epoxy r finishing resin like TJ mentions fuel proofs it and adds some overall strength and binds all pieces together.  Good luck with it!
  Type at you later,
   Dan McEntee

[Gerald Arana]

Paul, If you think it isn't glued, or the glue is still "wet" try to take it apart and see what happens.

Long story short: In my wood shop class I glued two pieces of Oak ( or mahogany, can't remember which, doesn't matter) for a table top and discovered that I had gotten one of them
upside down after clamping them together and tried to pull them apart. It broke the wood after 5 minutes.........still couldn't get them apart! 

Unless you put too much glue on your parts, I'd say go with it.

With alaphatic resin, you can spread a "thin" coat of glue on both surfaces, wait 15 minutes (or until it is dry to the touch) and iron it on with your mono coat iron. I've done this with 1/16" sheeting and it works great!

Jerry

[frank mccune]

     No worries!  The adhesive will be stronger than the wood!

     In the past, I have laminated wood with this type of adhesive by placing it on both surfaces and permitting them to air dry. I got  the adhesive to “fire off” by joining the pieces and applying heat via my wife’s iron or by fitting the pieces together and placing them in a microwave oven for a few seconds.  Never had a failure!

[paulwells66]

well as long as some of you have gotten away with it Im happy since I usually have good luck
Thanks for all the input...I did in fact clamp it with a hardwood spreader for 24 hours so should be good.

[BillP]

No worries.

[Scott Richlen]

Paul:

Don't worry about it!  The aliphatic will hold just fine.  There is no reason to use epoxy: it is heavy, it won't bond any better than aliphatic, and the wood will break first in either case.

Just make sure you fuel-proof your engine compartment: the same auto clear-coat you finish with will do that fine.  If you don't use a clear-coat, just use finishing epoxy.  Heat it a little so it is thin and penetrates well. 

[L0U CRANE]

It's not oxygen, but the air itself that begins the ultimate cure. Aliphatic resin glues are water-thinned as packaged, but waterproof when cured

...Seem to recall that aliphatic resin glues go through a chemical change when or after the water evaporates. That takes time, unless it is accelerated. As mentioned, heat can complete the reaction almost  instantaneously. I've used this for years, usually on wing leading edge sheeting, occasionally on capstrips or other thin wood over other structure. Heat penetrates thin wood better.

It's no special thing for a wood-glue bond to be strong enough to tear wood out on either or both sides of the joint. Even Ambroid or SigMent can do that on balsa.

When I use this technique, I wet one surface with aliphatic glue sparingly only along the wood to wood joint. Test fit them, just enough to mark the mating piece very slightly. Redraw a small line of Aliphatic: a small squeeze bottle or syringe with a fine tube like for CyA works. When the glue line has been transferred to the mating piece. Then sparingly renew-rewet the glue line. Wipe that glue off. Only not-quite-dry mating sectors remain at the glue joint .

Assemble the "under and over" pieces - and I emphasize: clamp/block/jig  exactly in final alignment. With a Monokote-type iron press, heat through to the joints. Done right, you'll hear a small puff/hiss when [b all[/b] the water is driven out. The joint is then permanent and - apparently- as strong as it would be after a week of room-temperature cure. The only way to realign the glued pieces then  involves knives or saws!

OBTW - this can work with thin plywood doublers, but 3/32" may be as thick as you could use, A lot of heat and pressure may be needed over the glue area .

[Will Hinton]

One great property with aliphetic is the ability to debond it with heat should the need ever arise.  Of course, with balsa you would likely torch the balsa to flame before getting the glue soft enough to seperate but with hardwoods it works fine.  I have had maple discolor when doing that, but still debonded fine and could be realigned and reglued sucessfully.

[Dave Harmon]

what did people use in the 50's? assuming there was no epoxy back then

Ambroid.
I never had a problem.

These days I use epoxy on motor mounts....Elmer's Carpenter glue on most of the rest of the airplane.
This stuff sands very well and dries pretty quick....cheap too. I just bought another 16oz bottle the other day at ACE Hardware....about $5

[Brett Buck]

On my super combat streak I used alphatiac resin to glue the engine beams (hardwood) to the fuselage doublers. Trying to keep it light.
I've read posts where people say to use epoxy instead but when I look at woodworking sites they claim it's stronger than the wood itself.
I also used it to secure the plywood bellcrank platform.

has anyone done this and did it fail or was it ok?

  It's fine and you will have no problems with it. As above, people built lots of complete airplanes with Ambroid, which is near the bottom of the list as far as desirability goes, and they held together long enough.

    Brett